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Merged
merged 1 commit into from
Sep 9, 2023
Merged

modexp: Fuzz failure 5-3 #267

merged 1 commit into from
Sep 9, 2023

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mratsim
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@mratsim mratsim commented Sep 8, 2023

In the test case, at the location:

constantine/constantine/math_arbitrary_precision/arithmetic/bigints_views.nim

Lines 166 to 178 in 1ad8499

let qBits = mBits-ctz
let pBits = 1+ctz
let qWords = qBits.wordsRequired()
let pWords = pBits.wordsRequired()
var qBuf = allocStackArray(SecretWord, M.len)
var a1Buf = allocStackArray(SecretWord, M.len)
var a2Buf = allocStackArray(SecretWord, pWords)
var yBuf = allocStackArray(SecretWord, pWords)
var qInv2kBuf = allocStackArray(SecretWord, pWords)
template q: untyped = qBuf.toOpenArray(0, M.len-1) # TODO use qWords instead of M.len
template a1: untyped = a1Buf.toOpenArray(0, M.len-1)

We use q.len == M.len instead of the exact q length needed as derived by mBits-count of trailing zeros.
That was a workaround used while waiting to fix an issue.
Unfortunately the higher words were left uninitialized.

@mratsim mratsim changed the title Fuzz failure 5-3 modexp: Fuzz failure 5-3 Sep 8, 2023
@mratsim mratsim merged commit f3a5f35 into master Sep 9, 2023
@mratsim mratsim deleted the fuzz-5-3 branch September 17, 2023 16:49
@mratsim mratsim mentioned this pull request Oct 9, 2023
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